FIG. 10 is a schematic diagram for explaining a conventional stereoscopic image display apparatus as disclosed in the Japanese Patent Application; Tokkai-Hei 5-244643.
The stereoscopic image display apparatus is provided with a display unit 101 of the movable video projector having two optical systems for projecting the parallax image, and the large-diameter convex lens 102 for focusing the projected image on each right and left eyes of the viewer.
In this apparatus, by provided with the convex lens 102 between the display unit 101 providing a pair of the movable projector which is able to project the stereoscopic image and the viewer 103, it distributes the stereoscopic image to both eyes of the viewer. Then, the optical sensor (not shown) provided near the display unit 101 captures the position of the viewer 103, so that the display unit 101 moves mechanically to focus the image on the eyes of the viewer 103.
However, in the conventional stereoscopic image display apparatus there is a drawback explained below. Though the stereoscopic image display apparatus moves in accordance with the movement of the viewer, the stereoscopic image is not captured by both eyes of the viewer 103 when viewer's is head is not horizontal, so that when he/she tilts his/her head to the screen he/she can not observe the image.
FIG. 11 is a conceptual diagram showing another conventional stereoscopic image display apparatus as disclosed in the Japanese Patent Application, Tokkai-Hei 7-13105. The stereoscopic image display apparatus comprises a screen 112 comprised of a diffuse transmission layer and two lenticular lenses sandwiching the layer, and a movable stereoscopic image projector 111 comprised of a right image projector 111R and a left image projector 111L.
The apparatus is provided with the stereoscopic instrumentation unit 114, which determines the perspective and the positions of both eyes of the viewer 113, and making the projector 111 track the movement of the viewer 113. Thus the viewer 113 circumvents constraints of his/her position. Further, since the right and left image projectors 111R, 111L are each independently movable, it enhances the degree of flexibility of the posture of the viewer.
When the viewer tilts his/her head, the conventional stereoscopic image display apparatus as described above tracks the tilt by shifting the right and left image projectors 111R, 111L in the vertical direction. However, in general the stereoscopic image contains only information of parallax between views of the left and right eyes. So that, the more the viewer tilts his/her head, the more the fusion of the stereoscopic image and the stereoscopic view will become difficult.
As described above, in the conventional stereoscopic image display apparatus, the projector moves in tracking movements of a viewer so that the right image is always captured by his/her right eye, and the left image is always captured by his/her left eye. However, the conventional stereoscopic image display apparatus can not track the tilting of the viewer's head. Provided if it could track the tilting, not only it actually fails to provide the viewer with any stereoscopic views, but also it fails to correctly fuse right images and left images with each other, thus viewers observe a double image.